Not bad. But I would change out the case for one without a power supply and get a quality PSU like the Rosewill RE502 500W or a FSP AX500-PN 500W. The one included with the case is weak on the 12V rail and is of questionable quality.

Take it easy there kiddo, Rome wasn't built in one day. Anyways, as long as the card has the correct drivers for vista (which most should) it should work with Vista. Nvidia is generally much better at drivers, than ATi. With the DX-10 card you only give up DX-10 capability. Since future games will be DX-10 and DX-9 your ok for gaming for a while too, it will be a while before it goes all out DX-10.

Personally I am completing my new build and went with a DX-9 card, since it far out performed DX-10 counterparts pricewise. From what I have seen the mid range DX-10 cards won't be able to play upcoming DX-10 games with suitable play rates and enjoy the DX-10 affects.